Ecological Risk Assessment of Heavy Metals in Sediment from Oil-producing Regions of Ilaje Local Government Area of Ondo State, Nigeria.

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International Journal of Research and Scientific Innovation (IJRSI) | Volume VI, Issue VI, June 2019 | ISSN 2321–2705

Ecological Risk Assessment of Heavy Metals in Sediment from Oil-producing Regions of Ilaje Local Government Area of Ondo State, Nigeria.

Adetola M. Olatunji-Ojo1*, Josephine O. Olayinka-Olagunju1, Dominic O. Odedeyi2 and Aderotimi Adejuyigbe2

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1Environmental Biology Unit, Department of Animal and Environmental Biology, Faculty of Science, Adekunle Ajasin University.
2Fisheries Unit, Department of Animal and Environmental Biology, Faculty of Science, Adekunle Ajasin University

Abstract -Nigeria is one of the developing countries that depend largely on oil exploration as major source of revenue for economic development. More than 400,000 tons of oil had spilled into the creeks and soils of most oil producing communities in Nigeria, thereby, affecting the livelihood of host communities. The study aimed at evaluating the present health status of water bodies proximate to oil wells located in Ilaje communities using six pollution indices which comprises of three single pollution indices {Contamination Factor (CF), Ecological Risk Factor (Er) and Index of Geo-accumulation (Igeo)} and three Integrated pollution indices {Pollution Load Indices (PLI), Potential Ecological Risk Index (RI) and Nemerow Pollution Index (Pnemerow)} to quantify the extent or degree of heavy metal contamination in the sediment. Eight (8) heavy metals (Cd, Fe, Cu, Pb, Ni, Mn, Cr, and Zn) from sediment taken for five (5) months from three different regions of Ilaje (Ayetoro, Orereara and Abereke) were analyzed using Atomic Absorption Spectrophotometer. Heavy metal concentrations range from: Cd (0.0607- 0.1067ppm), Fe (152.5404- 246.713ppm), Cu (0.5339- 1.3073ppm), Pb (0.2612- 0.5226ppm), Ni (0.1370- 0.2339ppm), Mn (0.5643- 0.7345ppm), Cr (0.1785- 0.2423ppm), Zn (1.0753- 1.7945ppm). All values were below the international standard for sediment and the pollution indices also reveals that the areas are not polluted with low potential ecological risk. Result of Pnemerow indicates the areas as safe domain for most benthic organmisms. Continuous monitoring of these areas, especially when there is oil spillage, is therefore, recommended.

Keywords: Heavy metals; Sediment; Pollution indices; Ilaje; Oil spillage

I. INTRODUCTION

Environmental degradation as a result of oil exploration is one of the major problems faced by oil producing communities. This problem has been prevalent in Nigeria since1950s and more than 400,000 tons of oil had spilled into the creeks and soils of southern Nigeria as a result of several factors including overexploitation, corrosion and vandalisation of pipe lines, illegal mining activities [1],[2].Apart from degradation of water quality, contamination of sediment with heavy metals is a major environmental threat to most benthic organisms